The color of the blood is RED, the color of the vein is bluish color, that is why it looks like your blood color is blue when you look at them. If you heard of a story that your blood turns color RED when your blood is exposed to oxygen, that is incorrect.
Prisoners on the hulks did nothing. they were moored in the hulks on the Thames, so were kept under lock and key, where they were not permitted anything by way of entertainment unless they were one of the few who warranted a visit from friends or family.
The determination of blood's color will depend on if there is oxygen in the blood or not oxygenated blood is a dark red color, the same color of the blood that comes out of am open scratch, Or Blue if it has little to no oxygen at all